For a visiting tourist, Mexico City is far nicer than you would probably expect. The historic center is busy and packed with great hotels and restaurants, while the district of Zona Rosa (the pink zone) is more upscale and corporate. The Condesa and Roma districts are more interesting and quite artsy, so there are plenty of areas to choose from. One warning though, almost no one in Mexico City speaks English, unless they are employed at a tourist hotel or upscale restaurant.
Hotels and hostels in Mexico City can offer good value, though on the lower end of things you might find the standards to be below what you are used to. Food and drinks can be very cheap if you concentrate more on street stalls and places that cater to locals. If you insist on places with English-language menus then you might find the city to be fairly expensive because those are mainly found within expensive hotels. If you bring a menu-translation app you’ll be able to confidently order at almost any restaurant and get great meals at low prices.
Fortunately most of the main attractions are free or rather cheap, and city tours are quite affordable as well. This is really a city where you can get by on nearly any kind of budget as long as you are crafty enough to find your comfort zone. The hop-on, hop-off bus tour lasts around 3 hours and is an excellent introduction and very good value.